Fixed nits

ctru-rs/examples/audio-filters.rs

@@ -41,23 +41,6 @@ fn main() {
     let apt = Apt::init().expect("Couldn't obtain APT controller");
     let _console = Console::init(gfx.top_screen.borrow_mut());
 
-    let mut ndsp = Ndsp::init().expect("Couldn't obtain NDSP controller");
-
-    // This line isn't needed since the default NDSP configuration already sets the output mode to `Stereo`
-    ndsp.set_output_mode(OutputMode::Stereo);
-
-    let channel_zero = ndsp.channel(0).unwrap();
-    channel_zero.set_interpolation(InterpolationType::Linear);
-    channel_zero.set_sample_rate(SAMPLE_RATE as f32);
-    channel_zero.set_format(AudioFormat::PCM16Stereo);
-
-    // Output at 100% on the first pair of left and right channels.
-
-    let mut mix: [f32; 12] = [0f32; 12];
-    mix[0] = 1.0;
-    mix[1] = 1.0;
-    channel_zero.set_mix(&mix);
-
     let mut note: usize = 4;
 
     // Filters
@@ -77,14 +60,30 @@ fn main() {
     // effectively streaming an infinitely long sine wave.
 
     let mut audio_data1 = Box::new_in([0u8; AUDIO_WAVE_LENGTH], LinearAllocator);
-    fill_buffer(&mut audio_data1[..], NOTEFREQ[4]);
+    fill_buffer(audio_data1.as_mut_slice(), NOTEFREQ[4]);
 
-    let mut audio_data2 = Box::new_in([0u8; AUDIO_WAVE_LENGTH], LinearAllocator);
+    let audio_data2 = audio_data1.clone();
-    fill_buffer(&mut audio_data2[..], NOTEFREQ[4]);
 
     let mut wave_info1 = WaveInfo::new(audio_data1, AudioFormat::PCM16Stereo, false);
     let mut wave_info2 = WaveInfo::new(audio_data2, AudioFormat::PCM16Stereo, false);
 
+    let mut ndsp = Ndsp::init().expect("Couldn't obtain NDSP controller");
+
+    // This line isn't needed since the default NDSP configuration already sets the output mode to `Stereo`
+    ndsp.set_output_mode(OutputMode::Stereo);
+
+    let channel_zero = ndsp.channel(0).unwrap();
+    channel_zero.set_interpolation(InterpolationType::Linear);
+    channel_zero.set_sample_rate(SAMPLE_RATE as f32);
+    channel_zero.set_format(AudioFormat::PCM16Stereo);
+
+    // Output at 100% on the first pair of left and right channels.
+
+    let mut mix: [f32; 12] = [0f32; 12];
+    mix[0] = 1.0;
+    mix[1] = 1.0;
+    channel_zero.set_mix(&mix);
+
     channel_zero.queue_wave(&mut wave_info1);
     channel_zero.queue_wave(&mut wave_info2);
 
@@ -106,7 +105,7 @@ fn main() {
         if keys_down.intersects(KeyPad::KEY_DOWN) {
             note = note.saturating_sub(1);
         } else if keys_down.intersects(KeyPad::KEY_UP) {
-            note += 1;
+            note = std::cmp::min(note + 1, NOTEFREQ.len() - 1);;
         }
 
         let mut update_params = false;
@@ -127,9 +126,6 @@ fn main() {
             update_params = true;
         }
 
-        // Check for upper limit
-        note = std::cmp::min(note, NOTEFREQ.len() - 1);
-
         println!("\x1b[4;1Hnote = {} Hz        ", NOTEFREQ[note]);
         println!("\x1b[5;1Hfilter = {}         ", filter_names[filter]);
 
@@ -152,7 +148,7 @@ fn main() {
 
         let status = current.get_status();
         if let WaveStatus::Done = status {
-            fill_buffer(current.get_mut_buffer(), NOTEFREQ[note]);
+            fill_buffer(current.get_buffer_mut(), NOTEFREQ[note]);
 
             channel_zero.queue_wave(current);
 

ctru-rs/src/services/ndsp/mod.rs

@@ -6,6 +6,8 @@ use crate::services::ServiceReference;
 
 use std::sync::Mutex;
 
+const NUMBER_OF_CHANNELS: u8 = 24;
+
 #[derive(Copy, Clone, Debug)]
 #[repr(u32)]
 pub enum OutputMode {
@@ -64,7 +66,7 @@ impl Ndsp {
     ///
     /// An error will be returned if the channel id is not between 0 and 23.
     pub fn channel(&self, id: u8) -> crate::Result<Channel> {
-        if id > 23 {
+        if id >= NUMBER_OF_CHANNELS as u8 {
             return Err(crate::Error::InvalidChannel(id.into()));
         }
 
@@ -216,7 +218,7 @@ impl AudioFormat {
 
 impl Drop for Ndsp {
     fn drop(&mut self) {
-        for i in 0..24 {
+        for i in 0..NUMBER_OF_CHANNELS {
             self.channel(i).unwrap().clear_queue();
         }
     }

ctru-rs/src/services/ndsp/wave.rs

@@ -26,8 +26,10 @@ impl WaveInfo {
         audio_format: AudioFormat,
         looping: bool,
     ) -> Self {
-        let nsamples: usize = buffer.len() / (audio_format.sample_size() as usize);
+        let sample_count: usize = buffer.len() / (audio_format.sample_size() as usize);
 
+        // Signal to the DSP processor the buffer's RAM sector.
+        // This step may seem delicate, but testing reports failure most of the time, while still having no repercussions on the resulting audio.
         unsafe {
             let _r = ctru_sys::DSP_FlushDataCache(buffer.as_ptr().cast(), buffer.len() as u32);
         }
@@ -38,7 +40,7 @@ impl WaveInfo {
 
         let raw_data = ctru_sys::ndspWaveBuf {
             __bindgen_anon_1: address, // Buffer data virtual address
-            nsamples: nsamples as u32,
+            nsamples: sample_count as u32,
             adpcm_data: std::ptr::null_mut(),
             offset: 0,
             looping,
@@ -56,7 +58,11 @@ impl WaveInfo {
         }
     }
 
-    pub fn get_mut_buffer(&mut self) -> &mut [u8] {
+    pub fn get_buffer(&self) -> &[u8] {
+        &self.buffer
+    }
+
+    pub fn get_buffer_mut(&mut self) -> &mut [u8] {
         &mut self.buffer
     }
 
@@ -64,7 +70,7 @@ impl WaveInfo {
         self.raw_data.status.try_into().unwrap()
     }
 
-    pub fn get_sample_amount(&self) -> u32 {
+    pub fn get_sample_count(&self) -> u32 {
         self.raw_data.nsamples
     }
 
@@ -78,7 +84,7 @@ impl WaveInfo {
 }
 
 impl TryFrom<u8> for WaveStatus {
-    type Error = String;
+    type Error = &'static str;
 
     fn try_from(value: u8) -> Result<Self, Self::Error> {
         match value {
@@ -86,7 +92,7 @@ impl TryFrom<u8> for WaveStatus {
             1 => Ok(Self::Queued),
             2 => Ok(Self::Playing),
             3 => Ok(Self::Done),
-            _ => Err(String::from("Invalid WaveInfo Status code")),
+            _ => Err("Invalid WaveInfo Status code"),
         }
     }
 }
@@ -105,7 +111,8 @@ impl Drop for WaveInfo {
         }
 
         unsafe {
-            // Result can't be used in any way, let's just shrug it off
+            // Flag the buffer's RAM sector as unused
+            // This step has no real effect in normal applications and is skipped even by devkitPRO's own examples.
             let _r = ctru_sys::DSP_InvalidateDataCache(
                 self.buffer.as_ptr().cast(),
                 self.buffer.len().try_into().unwrap(),